This invention relates generally to the field of printing presses, and more particularly to an improved bearing for supporting ink transfer rollers in which the useful life thereof has been substantially extended and the cost of manufacture significantly reduced.
In the construction of high speed printing presses such as those used in the newspaper industry, there are normally present one or more so-called ink transfer rollers used to transfer ink from an inked roller to an impression roller which then applies the ink in a predetermined pattern to a web of paper. In such presses, the roller is normally the width of the printed web, and of effective diameter slightly more than four inches. In operation, the roller executes not only rotational motion about the principal axis thereof, but, under the influence of a camming guide, it also executes axially oriented reciprocation over a path of travel of several inches. The roller operates in an atmosphere of fluid printing ink, water, and a surfactant which is continuously coated on the outer surface thereof, and substantially removed during transfer. Excess ink and contaminants continuously flow from the ends of the roller, and a substantial amount collects on the metal shaft which forms the core of the roller. In printing presses in use in the newspaper field, the roller is supported by journaling the shaft in roller bearings which permit not only rotation but the reciprocation abovementioned. As the printing ink contains carbon black and other solid particles flowing into the bearing with each reciprocating movement, an obvious effect is the shortening of the useful life of the bearing to as little as several weeks of continuous operation. While the cost of replacement bearings is not normally large, the cost of replacement includes the labor of at least partially disassembling and reassembling the press, and the downtime which is lost from the standpoint of production. In bearings of the type used in such apparatus, it is not possible to employ seals which are adapted to prevent the ink flow, and the bearing must provide a draining function as well as the normal support function. In commonly used roller type bearings the waste ink does not provide a lubricant, but an abrasive which causes the rollers to wear at a relatively high rate. Where lubrication is originally provided, the ink tends to wash this lubrication away as it flows through the bearing.